After all of the breathless forecasts of snow and ice this week, it was good ol' made-in-Oregon rain that brought traffic to a foggy-window standstill in the Portland region.

Thursday's winter deluge created the worst day of commuting in recent memory. From Hillsboro to the Hawthorne Bridge, flooding, mud, rocks, toppled trees and sinkholes jammed up motorists and transit riders.

But many weekday travelers can also blame themselves for the immobile mess, say experts on commuting culture.

For starters, Oregon and southwest Washington drivers are so accustomed to the rain that they often poo-poo it's potential wrath. "Everyone thinks snow is the big deal," said Earl Baker, auto repair coordinator for AAA of Oregon and Idaho. "But rain is really the big threat. 'Rain. No problem,' we tell ourselves. We're often proven wrong."

With the Big Wet expected to continue pounding the region over the next five days, commuters should also be mapping out "Plan B escapes" from their daily routes, said Philip Reed, senior consumer editor for the popular auto-advice website Edmunds.com.

"How many commuters really have a thought-out Plan B path that they can fall back on?" Reed said. "I mean one that's not bouncing around in your head but has been mapped out on Google Maps or with different transit schedules."

Tips for commuting in the rain

* Develop a Plan B. You're usual route could be blocked by a landslide or be underwater.

* Ride TriMet? As hard as it may be these days, try to find an alternate line. Most importantly, during storms, try to catch an earlier bus.

* Check TriMet.org and TripCheck.com before leaving.

* Go slow. It takes longer to stop or adjust in wet weather.

* Don't drive through moving water, especially if you can't see the ground under it. Cross large puddles with caution. They could be deeper than they appear. The water could stall and damage your engine. Also, most flood deaths occur in vehicles.

* Stay in the middle lanes on highways. Pooling water poses the threat of hydroplaning.

Judging from Thursday's rippling, crippling traffic jams, a lot of people haven't bothered.

Take Oregon 43 south of Portland's Sellwood Bridge. A tree fell from saturated, shifting soil into the heart of the morning commute. The Oregon Department of Transportation closed the highway for about 40 minutes to clear the debris.

However, scores of drivers who swear by 43 seemed to stick with 43, despite warnings or radio and local news sites about the hazardous debris. Drivers reported travel times of two hours or more to get from Lake Oswego to Portland.

Elsewhere, transportation officials said traffic patterns showed no indications that commuters were leaving home early or diverting from their usual routes to avoid flooding and rockslide on busy streets.

Water on the roadway on Oregon 99E, Southeast Milwaukie Avenue and Powell Boulevard created a ripple of gridlock east of the Willamette River that stretched from the Hawthorne Bridge to Sellwood.

"An hour and 20 minutes to go from Milwaukie to downtown – about 11 miles – and there were no accidents," said Gina Storey, an information technology recruiter. "Just plain slow."

She didn't have a Plan B. "Have never needed one. This morning was extraordinarily bad," she said.

Although U.S. 26 was a slog, traffic volumes on Interstates 5, 205 and 84 were about the same as most weekdays, indicating that drivers weren't using them as alternate routes.

Hundreds of TriMet drivers found themselves stuck on buses in the middle of the soggy traffic jams. Some escaped when they saw the chance. On Twitter, someone reported: "People so frustrated by #traffic they're getting off #trimet #19 and walking."

Of course, as Meghan Humphreys found, sometimes a good Plan B leads right into gridlock.

"I geared up to bike in the driving rain," said Humphreys, who works at EarthShare Oregon, "but I got a flat at Southeast 52nd and Clinton" in Portland. Ironically, that was also the location of sinkhole that was tying up traffic in the area.

Humphreys jumped on a TriMet bus. "Then I sat on the No. 14 bus for one hour."